Components on printed circuit board assemblies are frequently soldered into place using a solder fountain machine. For example, such solder fountain machines provide molten solder and urge the solder into contact with the electrical leads of electronic components such as integrated circuit chips. Also, solder fountain machines are used to connect various mechanical and electromechanical components to printed circuit boards (e.g., brackets, connectors, resistors, capacitors, etc.). Such solder fountain machines have been advantageously used in the past as an efficient tool for producing printed circuit board assemblies.
One example of a solder fountain technique will be described with reference to FIG. 1 to illustrate disadvantages that may be associated with conventional solder fountain techniques. The printed circuit board assembly 10 illustrated in FIG. 1 includes a printed circuit board 12. An electronic component 14 having component leads 16 is connected to the printed circuit board 12 by means of a solder fountain machine. Electronic component 14 is positioned adjacent a surface of the printed circuit board 12, and adjacent electronic components 18 are positioned adjacent an opposite surface of printed circuit board 12. The component leads 16 of electronic component 14 extend through printed circuit board 12 so that they can be connected by solder at the opposite side.
Using solder fountain head 20, molten solder is urged upwardly, thereby producing solder overflow 22. Although the solder contacts the component leads 16 of electronic component 14 so as to create a solder bond between the electronic component 14 and the printed circuit board 12, it has been recognized that solder overflow 22 sometimes contacts adjacent electronic components 18. An example of such solder overflow spilling onto adjacent components is illustrated at location 24 in FIG. 1.
Because it has been recognized that solder may spill onto an adjacent component such as at location 24, there is a limit as to how close adjacent components may be placed to one another when fountain soldering techniques are utilized. This limit is reached, for example, when overflow from the solder fountain spills onto adjacent components during soldering processes. It will be appreciated that contact between hot solder and electronic component bodies is highly undesirable. As such, component spacing on printed circuit board assemblies has been limited in that it cannot be smaller than the distance at which solder overflow begins to spill onto adjacent components.
In an attempt to overcome this acknowledged problem, it has been proposed to apply tape to the adjacent components before soldering. The tape is intended to prevent direct contact between the solder and the adjacent components during fountain soldering procedures. Referring to FIG. 2, for example, a printed circuit board assembly 100, like printed circuit board assembly 10, includes a printed circuit board 112 to which an electronic component 114 having component leads 116 is mounted. Electronic components 118 are mounted adjacent to electronic component 114 on the opposite surface of printed circuit board 112. A solder fountain head 120 produces solder overflow 122. Unlike circuit board assembly 10, printed circuit board assembly 100 includes high temperature tape 126 over each of the adjacent electronic components 118. As is illustrated at locations 124, solder overflow spills onto the tape 126, and the tape 126 is intended to prevent direct contact between the solder and the adjacent electronic components 118.
The use of tape for masking adjacent components has several shortcomings. Firstly, the use of masking tape such as tape 124 is associated with a high labor cost. The tape can be difficult to apply, and it should be applied to every component by a skilled technician. The use of masking tape is also associated with increased manufacturing time because the masking operation requires significant time for both tape application and removal processes. The tape masking procedure is also associated with questionable reliability in that the tape does not always stay in place during the soldering process. Accordingly, if the tape allows solder to contact the body of an adjacent component, that component may require replacement. The use of tape for masking also has questionable effectiveness in that the tape has limited thermal insulative properties. For example, if significant heat passes through the tape, it could damage the component even if the molten solder does not directly contact the component.
Accordingly, there remains a need for an apparatus and method for soldering that can overcome the disadvantages associated with prior art soldering techniques.